Measurement of the complete 3-component electric (E-) field vector has very recently become possible through the development of sensors that can measure free-space electric potential at the sub-microvolt level. This technology has been applied to through-clothing measurement of ECG, with successful preliminary measurements for EEG and ERP. Analysis has already shown that the normal E-field, En, produced by brain sources is more tightly focused in space than the tangential field from the same source when measured through the head. The goal of Phase I is to quantify how a measurement of the E-field in the direction normal to the scalp can be applied to replace or augment conventional electric potential data collected on the scalp surface. 3 specific analysis issues of relevance for EEG, ERP brain source imaging will be investigated. Synthetic data, including sensor effects, will be generated by a sophisticated three-dimensional (3D) numerical simulation supported by analytic calculations. The benefit of measuring the E-field will be quantified by analyzing the data with and without the normal field information, using a modified form of the Brainstorm program. In Phase II, a new type of EEG electrode system that includes sensors of the normal electric field will be constructed together with algorithms that utilize the En information. The system will be directly compared with a 120- electrode Geodesic Sensor Net System on subjects participating in standard evoked potential and EEG experiments. The ability to measure the normal E-field external to the head provides an entirely separate new channel of information about the electrical sources in the brain. If successful this program will contribute to the whole art of EEG signal acquisition, providing a general advance in research and clinical measurement technology. In addition, because the method operates off the body, it should lead to greater patient comfort and facilitate non-medical applications of brain signal measurement, such as alertness monitoring and cognitive state assessment.